Automatic lifting device

ABSTRACT

A vacuum actuated lifting attachment for a hoist or crane in which the functions of gripping and releasing of generally flatsurfaced objects are accomplished by means of vacuum and atmospheric pressure applied to the flat surface of the object in response to relative movement between the lifting attachment and object, to cause sequential operation of valve means controlling the evacuation and venting of a vacuum chamber communicating with an elastomeric suction cup for gripping the object.

United States Patent [1 1 [111 3,785,691

Sperry Jan. 15, 1974 AUTOMATIC LIFTING DEVICE 1,294,203 2/1919 Hitchcock 294/64 R [75] Inventor: Gene Sperry, Salem, 111. Primary Examiner Evon C. Bhmk [73], Assignee: American Chain & Cable Co., Inc., Assistant Examiner-James L. Rowland Bridgeport, Conn. Attorney-James A. Davis et al.

[22] Filed: Aug. 7, 1972 ABSTRACT [21] Appl' 278568 A vacuum actuated lifting attachment for a hoist or crane in which the functions of gripping and releasing [52] us. Cl 294/64 R of generally fla d j ts are ac mplished y [51] Int. Cl. B66c 1/02 means of vacuum n mospheric pressure applied to [58] Fieldof Search 294/64 R, 64 A; the flat Surface of he object in response to relative 214/1 BS, 35 I), 650 5G movement between the lifting attachment and object,

to cause sequential operation of valve means control- [56] References Cit d ling the evacuation and venting of a vacuum chamber UNITED STATES PATENTS communicating with an elastomeric suction cup for 3,347,327 /l967 Engelen 294/64 R x gnppmg the Object 3,431,010 3/1969 Glanemann 294/64 R 3 Claims, 9 Drawing Figures PATENTEDJAM 1 51914 SHEET 3 BF 3 AUTOMATIC LIFTING DEVICE This invention relates generally to vacuum actuated lifting devices and more particularly to such devices in which vacuum gripping and release functions are automatically performed in accordance with the load lifting and non-lifting operation of the device.

Automatically controlled vacuum actuated lifting devices are known, but heretofore such developments of the prior art, as typified by US. Pat. No. 2,776,857 issued Jan. 8, 1957, and No. 3,431,010 of March 4, 1969, for example, have been marked by serious performance limitations and over-complicated mechanisms making improvement thereof desirable. Among the more glaring shortcomings of such prior developments are the utilization of a diaphragm in the vacuum chamber which is susceptible to serious wear problems and, therefore, presents serious limitations on dependability of operation creating a safety hazard in use. Additionally, the use of a diaphragm actuated vacuum chamber of finite capacity imposes serious limitations on the gripping capacity of the lifting device.

As a consequence of the foregoing noted limitations and deficiencies, among others, the present invention is directed to improvements thereover and, in brief, provides a simplified vacuum actuated lifting deivce for attachment to a hoist or crane utilizing a piston and cylinder arrangement in which the capacity of the vacuum generating chamber responds generally in direct proportion to the weight of the load being lifted so that as load increases, vacuum increases. Limitation on lifting capacity, however, is present by the design area of the vacuum gripping element which cooperates with the vacuum generating chamber. Improved and simplified valve means are embodied for effecting automatic application and release of vacuum forces without the need for manual interference; the operation of the valve means being effected in accordance with relative movement between the lifting cylinder and piston occasioned by the engagement of the lifting device with the object or load to be lifted.

It is an important object of this invention to provide an improved and simplified automatically operable vacuum actuated lifting device for attachment to crane or hoise equipment.

Another object of this invention is to provide an improved lifting device, as aforesaid, employing automatically operable valve means for controlling the evacuation and venting of a vacuum chamber therefor.

Another important object of this invention is to provide an improved vacuum actuated lifting device which is dependable in operation and exhibits economies of manufacture and maintenance.

' Having thus described this invention, the above and further objects, features, and advantages thereof will be recognized by those familiar with the art from the following detailed description of a preferred embodiment thereof illustrated in the accompanying drawings, the same constituting the best mode presently contemplated for enabling those skilled in the art to make and practice the same.

In the Drawings:

FIG. 1 is a top plan view of a lifting device according to this invention;

FIG. 2 is a front elevational view thereof;

FIG. 3 is an enlarged cross-sectional view with parts in full elevation taken substantially along vantage line 3-3 of FIG. 1 and looking in the direction of the arrows thereon;

FIG. 4 is a partial enlarged elevational view with portions thereof in section of the valve means and associated elements positioned for lifting operation;

FIG. 5 is a partial enlarged developed view of the cam means employed in the assembly illustrated in FIG. 4 taken substantially from vantage line 55 of FIG. 4 and looking in the direction of the arrows thereon;

FIG. 6 is another view similar to view 4 illustrating the positioning of the valve means and associated elements conditioned for disengaging the device from the load;

FIG. 7 is a view similar to FIG. 5 showing the operating relationship of the cam means as viewed from vantage line 7--7 of FIG. 6 and looking in the direction of the arrows thereon;

FIG. 8 is another view similar to FIG. 4 showing the relationship of the valve means and associated elements, in condition for actively releasing the device of this invention from the load; and

FIG. 9 is the schematic view similar to FIGS. 5 and 7 taken substantially along vantage line 9-9 of FIG. 8 and looking in the direction of the arrows thereon to illustrate the relationship of the cam means in the operating condition therefor as illustrated in FIG. 8.

Turning now to the details of the herein illustrated embodiment of this invention, initial reference is made to FIGS. 1 through 3. As therein illustrated, a lifting device indicated generally by numeral 20, comprises a lifting cylinder assembly 21 having a hoist ring 22 for attachment to hook means 23 of an overhead crane or hoist. A piston assembly 24 (see FIG.3) is mounted internally of the cylinder assembly and is attached to a gripper assembly 25 located coaxially beneath the cylinder assembly, by an intervening piston rod and plunger assembly 26. The latter assembly contains a cam actuated valve assembly 27, for selectively sealing off and venting the upper interior of the cylinder comprising a vacuum chamber which is coupled to the gripper assembly by an interconnecting conduit means 28.

Of the several above outlined general components of device 20, it will be recognized from FIGS. 2 and 3 in particular that the cylinder assembly 21 is made up of a main cylinder body 30, preferably of cast metal to formulate cylindrical sidewalls 31 having air cooling ribs 32 on its exterior circumference and defining with the top wall 33 thereof, an internal cylindrical chamber 34 which is closed over at its bottom side by a bottom plate 35 fixed to the bottom edge of the sidewall 31 as by cap screws 36 so as to seal internal chamber 34. The

top wall 33 of the cylinder body 30 is provided with four upwardly extending rib portions 37 disposed diagonally thereof along four quadrants to merge with a central cylindrical hub portion 38 having a central bore opening 39 (see FIG. 3). A diametrically extending recessed portion 40 is formed at the outer end of hub portion 38 directly beneath attachment block 41 affixed to the hub portion 38 as by a welding, cap screws, or similar fasteners. The hoist ring 22 is fastened to the block 41; the same comprising a continuous annular ring member for engagement by the hoist hook 23, as previously mentioned. Between the recessed portion 40 and the central bore opening 39 is a countersunk valve seat 42 respective of a vent valve 43 which has an enlarged end and seal at its upper end. Valve 43 floats freely in bore 39 with the seal thereof engaging the seat 42.

A vacuum gauge 45 is mounted on the upper side of top wall 33 for the cylinder, beneath a U-shaped guard bracket 46, the gauge communicating directly with the upper interior of chamber 34 in operation.

As previously noted, the piston assembly 24 is mounted within the upper interior of the cylinder assembly and, more specifically, is located at the upper end of chamber 34 therein being affixed to the upper end of the piston rod and plunger assembly 26. As shown best in the cross-sectional showing of FIG. 3, the piston assembly comprises a generally cylindrical metal piston plate having a diametrical dimension slightly less than the interior diameter of chamber 34 and carrying at its periphery a molded piston seal ring of annular configuration designated 51. The seal is fixed in an annular groove 52 formed inwardly of the outer periphery of the piston member 50 to present a depending elastic lip portion 53 thereof to the interior sidewall of chamber 34 with flexible sealed engagement. A vent passageway opening 54, comprising a cylindrical bore, is formed centrally of the piston plate 50 in registering alignment with the central bore 39 through the head end of the cylinder body.

The piston plate 50 is fixed concentrically over the upper end ofa tubular piston rod 55 comprising one element of the piston and plunger assembly 26; the piston rod 55 extending coaxially through chamber 34 and a cylinder opening 56 formed coaxially of a central hub portion 57 of the bottom plate 35. The outer walls of the piston rod 55 are closely fitted within and guided by a sleeve bushing 58 pressed into opening 56.

While the detailed particulars of the piston and plunger assembly 26 will be described more fully hereinafter, suffice it to say at this juncture that the same comprises the tubular piston rod 55 and a coaxially mounted cylindrical plunger rod or shaft 60 slightly movable within and relative to the lower end of the piston rod 55 between limits. To the latter end a pair of diametrically opposed slotted openings 61-61 are formed through the tubular sidewalls of the piston rod for engaging the ends of a cylindrical pin connector 62, which extends through the plunger rod 60 so that its opposite ends project outwardly into the opposed slotted openings 61-61 thereby to slidingly interconnect the cylindrical piston rod 55 and the plunger 60.

As noted previously, the gripper assembly 25 is mounted coaxially beneath the cylinder assembly and, more specifically, is fastened to the lower end of the plunger member 60 as best shown in FIGS. 2 and 3. As therein illustrated, the gripper assembly comprises a cast metal lift plate 65 having a generally circular body portion 66 formed with a chamfered periphery 67 and a centrally located upwardly extending cylindrical boss portion 68. Portion 68 is distinguished by a central bore 69 receptive of a ball ended connector stud 70 and a threading ball retainer sleeve 71 therefor whereby to provide a ball and socket or universal swivel connection between the plunger 60 and the lift plate. The stud connector 70 has a threaded shank 72 which receives a lock nut 73 and a lock washer 74, beneath a four armed generally U-shaped indicator bracket 75. Four upwardly extending arm portions 76 of the bracket pass outwardly along the exterior walls of cylinder body 30, passing through cutaway opening 77 (see FIG. 1) in the air-cooling ribs 32. The threaded shank 72 of the stud .and plunger assembly, the outer ends of the arm 76 thereof provide a visual indicator of the approximate location of the piston in chamber 34 thereby indicating the degree of operating vacuum to the user.

Mounted over the upper marginal portion and chamfered edge 67 of the lift plate is a resilient elastomeric seal ring 80 having an angularly depending seal lip portion 81 of tapered cross-sectional configuration for engaging the upper surface 82 of a planar work piece or object 83 to be lifted. Extending radially inwardly of the upper end of the seal rings lip portion 81 is an annular planar mounting flange portion 84 adapted to overlie the upper marginal surface 85 of the lift plate. An annular clamping ring 86 is mounted over the flange portion 84 and is held tightly thereagainst by a plurality of cap screw connectors 87 thereby securely fastening the seal ring 80 to the lift plate. It will be appreciated that the angularly extending lip portion 81 of the seal ring forms with the lift plate and the upper surface 82 of the work piece a generally truncated conical sub-chamber 90 forming a secondary vacuum chamber which communicates directly with the upper portion of the cylinder chamber 34 via the conduit means 28. Thus whatever vacuum or atmosphere is present in the upper end of chamber 34 is correspondingly produced in the secondary vacuum chamber 90 when the seal ring is engaged with the surface of the work piece. It further will be appreciated that on initial contact between the seal ring 80 and surface 82 of the work piece, slight downward movement of the gripper assembly toward the work piece serves to partially evacuate the sub-chamber 90 and effect an initial suction cup gripping action between the seal member 80 and the work piece 83. This initial gripping force, when reenforced by the evacuation of chamber 90 produces a powerful and positively regulated vacuum gripping connection between the gripper assembly 25 and the work piece.

With specific reference now to the conduit means 28, it will be recognized from FIG. 2 that connection of the upper interior of the cylinder chamber 34 is effected via an elbow member 92 threaded through an opening in the sidewalls 31 of the cylinder. Elbow 92 is joined to an air filter member 93 and a long rigid nipple or pipe 94 leading to a second elbow 95 located at the lower end of nipple 94. Elbow 95 in turn is coupled to flexible hose 96 by a clamp connector means 97. The lower end of the hose 96 in turn is connected to a third elbow fitting 98 mounted in an opening extending through the left plate 65 to communicate with the chamber 90 therebeneath. Thus, any atmosphere within the upper end of the cylinder chamber 34 is communicated directly to the chamber spacing 90 beneath the lift plate 65.

A suitable vent and air filter 99 is mounted in the lower bottom plate 35 of the cylinder assembly as at threaded opening 100 (see F IG. 3) whereby to vent the lower portion of chamber 34 beneath the piston assembly to atmosphere.

Referring again to the piston rod and plunger assembly 26, comprising the interconnected cylindrical piston rod 55 and plunger rod 60 previously described, it will be understood from FIG. 3, in particular, that the upper interior of the piston rod houses the valve assembly 27 which will now be described. Mounted over the upper end of the plunger rod 60 and more specifically pinned to an extending core portion 102 thereof by connector pin 103, is a lower cylindrical cam member 104 which is adapted to reciprocate with the latter within and relative to the piston'rod 55. Cam 104 is prevented from rotating relative to piston rod 55 by virtue of the connector pin 62 which rides in the slotted opening 61-61 as previously described. The upper end of the cam 104 is formed with a plurality of camming teeth 105 of like formation which extend around the upper end thereof, each of which is distinguished by elongated cam face 106 and a shorter cam face 107 (see FIGS. 59). The lower cam 104 is further provided with at least one elongated slotted opening 108 milled in its outer cylindrical wall for reception of an index pin 109 projecting through the sidewall of the tubular piston rod 55 at opening 110 (see FIGS. 4, 6 and 8).

Disposed coaxially over lower cam 104 is a similar upper cam 114. As will be noted best from FIGS. 5, 7 and 9, upper cam 114 is provided with a plurality of camming teeth 115 on its lower end, such teeth 115 being identical in formation to teeth 105 in the lower cam and therefore each comprising an elongated cam face or surface 116 intersecting a shorter cam face 117. For purposes which will appear presently, adjacent teeth of the upper cam in FIGS. 5, 7 and 9 are designated 115, 1150, 115b and 1156. It further is to be noted that the upper cam is distinguished by a plurality of elongated openings 118 (corresponding to openings 108 in the lower cam) and a plurality of shorter slotted openings 119; the openings 118 and 119 being formed at the base apex of alternately adjacent cam teeth for alternate sequential engagement with the index pin 109.

Rotatably and slidingly mounted on the upper cam 114 and extending coaxially upwardly therefrom is a valve means 120 having a cylindrical stem body 121 (see FIGS. 4, 6 and 8). The valve stem passes through a cylindrical bore 122 formed coaxially through the body of the upper cam member to communicate with an enlarged counterbore 123 opening inwardly of the lower end thereof. An annular spacer ring 124 is mounted over the valve stem body 121 beneath the bottom wall ofthe counterbore 123 and a snap retainer ring 125 engages a groove cut in the valve stem 121 to maintain the spacer in position. Thus, the valve stem is coupled with the upper cam member.

The upper or outer end of the valve stem 121 is distinguished by an enlarged cylindrical valve head portion 126 having a resilient seal 127 over its upper face. It will be appreciated that in assembly, the valve seal 127 effectively seals off the vent opening 54 formed coaxially through the piston body inasmuch as the diameter of the valve head and seal is greater than the diameter of the opening 54. Blocking opening 54, of course, prevents passage of air therethrough as is illustrated in FIG. 3, for example. For this purpose, a spring 128 closely surrounds the valve stem 121 between the lower face of its head 126 and the upper end of cam 114 to normally bias the valve head and stem portion away from the upper cam member.

In addition to spring 128, a larger upper cam spring 130 coaxially surrounds the valve stem and valve spring to extend between the lower face of the piston body 50 and the upper end of the upper cam member 114, being coaxially guided on the latter by reason of an annular guide recess 131 formed in the upper periphery of the cam member 1 14. The lower end of spring 130 rides on a washer 132 to assist rotation of cam 114 reative thereto. Spring 130 acts to normally bias the upper cam member downwardly away from the piston body and maintain the same tightly against the index pin in operation as the upper cam member is periodically rotatably indexed with counterclockwise movement (as viewed from above) as will appear in greater particular hereinafter.

It should be noted that the tubular piston member 55 is importantly provided with several ports or vent openings 135 spaced about its upper end immediately adjacent to the valve head 127. Additionally secondary vent openings 136 also are provided immediately of the ends of the piston rod to assist in the flow of air past the valve head in operation.

Having thus described the various elements which go to make up the improved lifting device 20 of this invention, the operational functioning thereof will now be described with particular reference to FIGS. 4 through 9 of the drawings. As shown best in FIG. 3, the device 20 is in a position to effect lifting of the work piece 83 with the valve means 120 positioned with its head seal 127 tightly over the vent openings 54. This prevents the inflow of air into the portions of cylinder chamber 34 above the piston assembly 24. The plunger member 60, in this position of operation, has previously drifted downwardly to its lower limit of movement relative to the piston rod 55 as dictated by the engagement of pin 62 with the bottom ends of the slotted openings 61. Thus, as the cylinder 30 moves upwardly with the hoist hook 23, the piston assembly 24 will be pulled downwardly with the piston rod 55, eventually assuming a position indicated schematically by the dotted lines shown in FIG. 3. This downward movement of the piston assembly 24, causes the atmosphere of chamber 30 thereabove to evacuate, pulling the vent valve means 43 tightly over seat 42 and closing passageway 39. The vacuum or subatmospheric pressure above the piston is then communicated via the conduit means to the subvacuum chamber between the gripper assembly and the work surface 82. In this fashion the work piece is tightly coupled to the gripper assembly and is raised with the hoist.

It will be recognized that the extent of the lowering movement for the piston 24 depends somewhat on the weight of the work piece 83 being lifted and that within the designed gripping limits of the assembly 25 based principally on engagement area of its flexible seal ring,

the greater the load the greater the evacuation of the chamber 34 above the piston. Consequently, with increased evacuation of the chamber 34 a corresponding increased evacuation of sub-chamber 90 beneath seal ring 80 occurs to provide commensurate increased gripping action with the work piece or load. This condition of operation is illustrated best in FIGS. 4 and 5 with the latter showing the relationship of the two cam members associated with the valve assembly 27. It is to be noted in particular from FIG. 5, that the index pin 109 is shown engaged with one of the shorter slotted openings 119 intermediate two adjacent teeth a and 115b of the upper cam in this operating condition. Thus, the cam spring is in a semi-compressed state and the valve spring 128 is compressed, tightly holding the valve seal 127 over the vent opening 54 during this first operational condition for lifting the work piece. Upon raising the load, piston rod 55 will move downwardly to draw a vacuum in the upper side of chamber 34.

In FIG. 6, a second operational condition is illustrated as occurs after the load has been lifted and moved to a designated resting position. Lowering action by the hoist effectively relieves the weight of the load or work piece from the lifting device 20. As this takes place, plunger rod 60, as illustrated in FIG. 6, moves upwardly within the cylindrical piston rod 55, forcing the lower cam 104 into engagement with upper cam 114 and fully compressing both the cam spring 130 and the valve spring 128. With such upward movement of the cams, particularly the upper cam 114, the index pin 109 is disengaged from the shorter slotted opening 119 (see FIGS. 4 and 5). Disengagement of the indexing pin and the inter-engagement of the cam teeth of the two cams, as shown in FIG. 7, causes the upper cam 114 to rotate relative to the lower cam 104; the latter being held against rotation by connector pin 62 while the index pin 109 moves into the elongated slotted opening 108 of the lower cam (see FIG. 6). It will be noted that the rotation imposed by tooth engagement serves to align a tooth (115b) of the upper cam over the index pin 109 (located in the slotted opening 108 of the lower cam). With the parts positioned as shown in FIGS. 6 and 7, the lifting device is now conditioned to release the work piece in response to raising movement of the hoist, a condition illustrated in FIGS. 8 and 9 of the drawings.

As shown in FIG. 8, for example, upward movement of the device relative to the work piece causes the plunger 60 to move downwardly relative to the piston rod 55; such downward movement being limited by engagement of the pin 62 with the bottom end of the slots 61 in the tubular piston rod. As this occurs, the lower cam 104 moves downwardly with the plunger rod and the cam spring 130 forces the upper cam downwardly against the index pin 109 which, it will be recalled from FIG. 7, is aligned substantially opposite the apex of one tooth, such as tooth 115b therein illustrated. Such engagement of the index pin causes the latter to move along the longer sloping face 116 of tooth 115b, rotating the upper cam 114 until the index pin enters the elongated slotted opening 118 adjacent tooth 115a. As soon as the pin 109 enters the elongated opening 118, the upper cam moves downward rapidly and in so doing disengages the valve means, more particularly the head and seal 126 and 127 thereof from the vent opening 54. This permits pressurized or atmospheric air within the lower portions of cylinder chamber 34 to flow through the vent openings 135 and 136, past the cam spring 130 and outwardly through the vent opening 54 to the upper side of the piston plate 50, or in other words, into the evacuated portion of chamber 34 above the piston, pressurizing the formerly evacuated portion of chamber 34. Pressurized air also flows upwardly through the central vent bore 39 in the top 0k head end of the cylinder, lifting the vent valve 43 from its seat 42 (see FIG. 3). By virtue of the interconnecting conduit means 28, of course, the subatmospheric chamber 90 beneath the gripper assembly 23 is also pressurized, thus releasing the vacuum grip with the surface of the work piece. Disengagement of the lifting device from the latter occurs upon continued upward movement of the device 20.

On the next upward stroke of the plunger rod 60, as will occur when resting the lifting device on the next sheet of material or work piece to be raised and moved, interengagement of the teeth of the two cams will again occur, causing partial rotation of the upper cam, to remove the index pin from a deep milled slot 118 thereof. As soon as the device is then lifted relative to the work piece, the downward travel of the plunger rod 60 disengages the lower cam from the upper cam, permitting the index pin to complete rotation of the upper cam and engage with the next succeeding milled slot, as for example, the shallow milled slot 119 to the left of tooth 1150 as viewed in FIG. 9. When this occurs, the valve means 127 will be positioned over the vent passageway 54 and the parts will be conditioned ready for lifting operation as viewed in FIGS. 4 and 5 of the drawings.

From the foregoing description, those familiar with the art will readily recognize and appreciate the simplicity of operation resulting from the improved arrangement of parts according to this invention which permits automatic evacuation, gripping, and disengagement of the vacuum gripper assembly in response to vertical up and down movements of the lifting device with the hoist without the need for manual turning of valves and the like, from a human operator. While this invention has been hereinabove described in associated with a preferred embodiment as illustrated in the drawings, it is to be recognized that its concepts and teachings are susceptible to variation and substitution of equivalents without necessarily departing from the scope of the herein described invention, as defined in the following appended claims.

I claim:

1. A vacuum actuated lifting attachment for coupling a hoist to flat surfaced objects comprising: a lifting cylinder attachable to the hoist for actuating movements thereby and enclosing an internal chamber, a piston assembly movable within said chamber, a gripper assembly exteriorly beneath said cylinder including resilient seal means for gripping and forming a sealed subchamber with a planar surface, a tubular piston rod and plunger rod assembly, interconnecting said piston and gripper assemblies, the piston rod being connected to said piston assembly and the plunger rod being connected to said piston rod and gripper assembly for reciprocating movement with and relative to said piston assembly, a pair of valve means, one on said cylinder and one associated with said piston assembly for controllably sealing and venting said chamber above said piston assembly, conduit means communicating between said sub-chamber and said chamber above said piston, and a pair of cam elements mounted within said piston rod, one being reciprocally movable with said plunger rod relative thereto and the other being rotatably driven by said one element to operatively control said valve means associated with said piston assembly in response to selected movement of said piston and plunger rods relative to one another and said cylinder whereby to selectively evacuate and vent said subchamber in response to selected actuating movements of said cylinder.

2. The invention of claim 1 and a pair of spring means in said piston rod, one opposing sealing operation of said valve means associated with said piston assembly and the other effecting said sealing operation thereof,

said spring means being controlled by axial positioning of said cam elements within said piston rod.

3. A vacuum actuated lifting device for automatically coupling and detaching flat surfaced objects to an overhead hoist comprising: a cylinder having top and bottom walls enclosing an internal chamber and including means for attaching the same to a hoist for vertical raising and lowering movements therewith, said top and bottom walls being provided with central passageways therethrough; first vent valve means mounted in the top wall passageway and operable to close and open responsively with the evacuation and pressurization of said chamber, piston means movably mounted in said chamber, including seal means engaging the internal side walls of the cylinder, said piston means having a vent opening communicating between the upper and lower sides thereof and said chamber being openly vented to atmosphere beneath said piston means; a tubular piston rod having its upper end fixed to said piston means so that its hollow interior communicates with said vent opening and said chamber above said piston means while the lower end thereof communicates with atmosphere beneath said piston means and slidably passes through the passageway in the bottom wall of said cylinder; a plunger rod, slidingly mounted within said piston rod for limited coaxial reciprocating movement relative thereto, said plunger rod extending beyond the lower end of said piston rod and cylinder; a gripper assembly connected to the lower end of said plunger rod for movement therewith and comprising an annular seal ring mounted for sealing engagement with the surface of an object to be lifted, conduit means communicating between the upper end of said chamber and a sub-chamber formed between said gripper assembly and the surface of an object engaged thereby, second vent valve means mounted within the upper end of said piston rod and provided with a head portion for sealing said vent opening and a stem portion depending therefrom, upper cam means rotatably and slidably connected to said stern portion and having a plurality of cam teeth at its lower end and a plurality of cam teeth at its lower end and a plurality of circumferentially spaced alternately long and short slotted openings formed in its exterior walls, each opening upwardly of the base apex between adjacent said teeth; an indexing pin projecting inwardly of the interior side walls of said piston rod means for engaging said slotted openings, first spring means biasing said second valve means toward said vent opening, second stronger spring means oppositely biasing said upper cam means away from said piston means whereby to resiliently engage said indexing pin; lower cam means connected to the upper end of said plunger rod for axial movement therewith and having a plurality of cam teeth at its upper end for engaging said teeth on said upper cam means in response to movement of said plunger rod toward said piston means, interengagement of said cam means serving to rotatably index said upper cam means to effect entry of said indexing pin into a said slotted opening upon subsequent disengagement of said cam means; engagement of said pin with said long and short slotted openings, respectively, serving to operate said second valve means to correspondingly open and close said vent opening whereby downward movement of said piston means with said vent opening therein closed serves to evacuate the atmosphere in a portion of said chamber above said piston while subsequent reversing movement of said piston means effects vent opening operation of said first and second valve means to vent said evacuated portion to atmosphere, thereby producing corresponding vacuum gripping and release of a said object by said gripper assembly.

'fgfgf 111111151) 5'111'1115 PATENT 01-1-1013 CEIHIFICAIE OF CORREClION 3,785,691 Dated January 15, 1974 Patent No.

Invcntoz-(s) GENE SPERRY It is certified that error appears in the above-identified patent and that said Letters Patent: are hereby corrected as shown below:

Title page [57] Abstract: 4th line, "pressure" should be" "pressures-- as on p. 1, line 7 of Application.

-Col. 1, line 45", "hoise" should be -hoistas on p. 2, line 19.

C01. 2, line 67, "respective" should be '-receptive as on p. 5, line Q01. 3, line 38, "slightly" should be --slidinglyason p. 6, line 6.

Col. 10, line 4, claim 3, "and aplurality of cam teeth at its lower end" is a repetition and should be deleted.

Signed and sealed this 25th day of 'June 19714..

(SEAL) Attest;

EDWARD M.FIJEI'CHER,JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents 

1. A vacuum actuated lifting attachment for coupling a hoist to flat surfaced objects comprising: a lifting cylinder attachable to the hoist for actuating movements thereby and enclosing an internal chamber, a piston assembly movable within said chamber, a gripper assembly exteriorly beneath said cylinder including resilient seal means for gripping and forming a sealed subchamber with a planar surface, a tubular piston rod and plunger rod assembly, interconnecting said piston and gripper assemblies, the piston rod being connected to said piston assembly and the plunger rod being connected to said piston rod and gripper assembly for reciprocating movement with and relative to said piston assembly, a pair of valve means, one on said cylinder and one associated with said piston assembly for controllably sealing aNd venting said chamber above said piston assembly, conduit means communicating between said sub-chamber and said chamber above said piston assembly, and a pair of cam elements mounted within said piston rod, one being reciprocally movable with said plunger rod relative thereto and the other being rotatably driven by said one element to operatively control said valve means associated with said piston assembly in response to selected movement of said piston and plunger rods relative to one another and said cylinder whereby to selectively evacuate and vent said sub-chamber in response to selected actuating movements of said cylinder.
 2. The invention of claim 1 and a pair of spring means in said piston rod, one opposing sealing operation of said valve means associated with said piston assembly and the other effecting said sealing operation thereof, said spring means being controlled by axial positioning of said cam elements within said piston rod.
 3. A vacuum actuated lifting device for automatically coupling and detaching flat surfaced objects to an overhead hoist comprising: a cylinder having top and bottom walls enclosing an internal chamber and including means for attaching the same to a hoist for vertical raising and lowering movements therewith, said top and bottom walls being provided with central passageways therethrough; first vent valve means mounted in the top wall passageway and operable to close and open responsively with the evacuation and pressurization of said chamber, piston means movably mounted in said chamber, including seal means engaging the internal side walls of the cylinder, said piston means having a vent opening communicating between the upper and lower sides thereof and said chamber being openly vented to atmosphere beneath said piston means; a tubular piston rod having its upper end fixed to said piston means so that its hollow interior communicates with said vent opening and said chamber above said piston means while the lower end thereof communicates with atmosphere beneath said piston means and slidably passes through the passageway in the bottom wall of said cylinder; a plunger rod, slidingly mounted within said piston rod for limited coaxial reciprocating movement relative thereto, said plunger rod extending beyond the lower end of said piston rod and cylinder; a gripper assembly connected to the lower end of said plunger rod for movement therewith and comprising an annular seal ring mounted for sealing engagement with the surface of an object to be lifted, conduit means communicating between the upper end of said chamber and a sub-chamber formed between said gripper assembly and the surface of an object engaged thereby, second vent valve means mounted within the upper end of said piston rod and provided with a head portion for sealing said vent opening and a stem portion depending therefrom, upper cam means rotatably and slidably connected to said stem portion and having a plurality of cam teeth at its lower end and a plurality of circumferentially spaced alternately long and short slotted openings formed in its exterior walls, each opening upwardly of the base apex between adjacent said teeth; an indexing pin projecting inwardly of the interior side walls of said piston rod means for engaging said slotted openings, first spring means biasing said second valve means toward said vent opening, second stronger spring means oppositely biasing said upper cam means away from said piston means whereby to resiliently engage said indexing pin; lower cam means connected to the upper end of said plunger rod for axial movement therewith and having a plurality of cam teeth at its upper end for engaging said teeth on said upper cam means in response to movement of said plunger rod toward said piston means, interengagement of said cam means serving to rotatably index said upper cam means to effect entry of said indexing pin into a said slotted opening upon subsequent disengagement of said cam means; engagement of said pin with said long and short slotted opeNings, respectively, serving to operate said second valve means to correspondingly open and close said vent opening whereby downward movement of said piston means with said vent opening therein closed serves to evacuate the atmosphere in a portion of said chamber above said piston while subsequent reversing movement of said piston means effects vent opening operation of said first and second valve means to vent said evacuated portion to atmosphere, thereby producing corresponding vacuum gripping and release of a said object by said gripper assembly. 